One function of a turbidity barrier is to control silt, pollutants and other unwanted substance sin or around water. In manufacturing a construction road, silt and other materials (including pollutants) are suspended in water that may naturally occur where the road is being built. Turbidity barriers are placed within the water to create a confined zone of contained materials.
Contained areas allow marine contractors to stay within Federal and State Clean Water Act and NPDES
Floating turbidity barriers (also known as curtains) are the most practical and economical way to control silt and turbidity while working in or around water. Silt, pollutant and sediment control created during dredging and marine construction activities are controlled. Floating turbidity curtains are sometimes called barriers and comply with government requirements regarding water pollution control. Most often these curtains are used in swamps, ponds, lakes, canals and waterways with light wind or current.
Turbidity barriers, also referred to as silt curtains, are floating barriers that are designed to control various sediments or runoff. There are a variety of calm water applications including but not limited to ponds, calm water lakes, swamps, construction sites, roadside construction projects, and protected inland areas.
So-called type 1 turbidity curtains are suitable for use in protected waters where the effects of wind, waves, and current are minimal. Usually, each section of a floating turbidity curtain includes PVC-coated polyester fabric, bottom tension/ballast member (usually a chain) for tying sections of the curtain together and foam flotation member (for instance 6 inch2 or 8 inch2 polystyrene in sealed float cavities). The float may be square, rectangular or cylindrical in cross section. Typically sections of the floating turbidity curtain are 50 or 100 feet long and sections are connected end to end. The ballast chain is shackled section-to-section on the turbidity curtains.
The ends of each section are typically tied together by lacing grommets with reinforced rope. Tension/ballast is usually galvanized steel chain. A grommet is a ring or edge strip inserted into a hole through plastic material which is used as the principal material in the turbidity barrier. Grommets are generally flared or collared on each side to keep them in place. Grommets are often made of metal, plastic, or rubber. They are used to prevent tearing or abrasion of the pierced material and they also protect the device used to secure one barrier section to another barrier section. The device used to secure the sections of the barrier together may be a wire, cable, rope or other material which penetrates the material of the section.
Barrier section lengths can be any length but typically are 50 feet or 100 feet long. The depth of the barrier can be selected. One such depth is 5 feet.
A variety of materials may be used for the curtain/barrier. For example, 18 oz/sq yd PVC laminated polyester fabric may be used. The curtain/barrier may include a filter fabric through a portion of the curtain/barrier.
So-called type 2 turbidity curtains are suitable for use in rivers, inland waterways, harbors, swamps, and lakes with wind and or current. The curtains control and contain silt and turbidity in moving water applications. Typically type 2 curtains use high strength fabric with heavy duty tension members and aluminum stress plates at the bottom skirt corners. These type 2 turbidity curtains are used in applications involving mild current and wind.
Heavier 22 oz/sq yd PVC-coated polyester fabric may be used in type 2 turbidity curtains. Type 2 turbidity curtains may use floats which are 6 inch2 to 10 inch2 in sealed float cavities. The float may be square, rectangular or cylindrical in cross section. The type 2 turbidity barrier may be use a galvanized steel cable polyethylene tube. A suitable bottom tension and ballast of sufficient strength is used. End connectors may be high strength aluminum located at the float and top tension cable. Lacing grommets are also used to secure barrier sections together. Chain ends are connected together at the bottom of the barrier sections. Steel cable contained in a polyethylene tube provides top tension and bottom tension and ballast is provided by a galvanized steel chain. End connectors at the float and top tension cable. Type 2 barriers are usually used with sections 50 to 100 feet length and can be deeper than the type 1 barriers.
Type 3 turbidity barriers are heavy duty use heavy duty tension members above and below the flotation and at the bottom of the curtain. Stress plates are at the bottom corners of the barrier sections. Type 3 curtains are used for silt, sediment control during dredging and marine construction activities in rivers, bays and waterways with moderate current, wind and wave activity. In general type 3 barriers may use components similar to the type 2 barriers with stronger or larger components. For example, heavier plastic fabric such as 40-oz PVC fabric may be used.